Linux raid mdadm mean of “Used dev size” Posted on December 26, 2015 by coder For RAID0, "Used Dev Size" does not exist. For RAID1, "Used Dev Size" equals to half of total disks' size. For RAID5, "Used Dev Size" equals to size that are used for parity. 123 For RAID0, "Used Dev Size" does not exist.For RAID1, "Used Dev Size" equals to half of total disks' size.For RAID5, "Used Dev Size" equals to size that are used for parity. TESTED !